The present invention relates to a transducer for electrical measurement of positive and negative extensions on cylindrical or profiled bodies, the transducer comprising more than two pieces and being essentially annular, with at least one clamping element, where two clampable segments each have, in their longitudinal centre on the inner contour and lying opposite each other in the clamping direction, a recess for a protruding resilient part with a measuring element, which recesses can be pressed by force onto the surface of the body.
Transducers are known which by cylindrical or strip-like resilient bodies generate a contact pressure sufficient to press the extension-sensitive measurement elements by force onto a hole wall. Such transducers are for example known from U.S. Pat. No. 5,284,062 which concerns a cylindrical object of elastomer material, and from CH, A 685575 which concerns the strip-like structure of the resilient part.
Other systems used today by means of belts or magnets clamp measurement bridges with blades at constant spacing onto the surface of flat or cylindrical objects and thus measure the extension occurring. The former transducers have the disadvantage that a hole must be made. The second said solution is very exposed, the measurement bridges can slip and are not therefore suitable for industrial use.
CH, A 687648 also describes a sensor with which the said disadvantages can largely be avoided as resilient elements on the inside of two half-rings press measurement elements onto the outer surface of the body so that the extension occurring there can be measured. These rigid transducers of a particular size are suitable only for a relatively small diameter range. Furthermore the measurement object must be precisely round in cross-section at the measurement point, and this sensor is not provided for angular profiles.
A variant of the sensor to CH, A 687648 has two rods with recesses which are approximately round which correspond at least to the cylinder to be measured. These sensors too are suitable only for a particular diameter range. In a cylinder with a diameter smaller than normal, the device can slip if conditions are unfavourable. This arrangement can also be sensitive to vibrations as generally there are no side guides.
Finally, sensors are known which by means of screws press two flat profiles containing resilient parts with extension-sensitive measurement elements onto a square profile so that the extension can be measured at this profile. This arrangement is, however, only suited for profiles with flat outer surfaces.